Many transport carriers, such as baby strollers, baby carriages and grocery carts are equipped with double wheel casters which provide greater ease and mobility when turning corners. The double caster wheels cause the transport carrier to be easier to push and provide greater stability to the transport carrier. However, prior art double wheel casters have a tendency to shimmy when the wheel speed exceeds a certain velocity. This could cause the transport carrier to become difficult to maneuver. Furthermore, undesirable vibrations may agitate the infant to the point where the infant has to be hand carried.
Prior art double wheel casters typically have their wheels freely rotatably supported on a support rod which is rotatably mounted on the carrier. Each wheel is capable of freely rotating on the support rod and with respect to each other. When a carrier is turning a corner at a relatively fast velocity, one of the wheels of the double wheel caster tends to turn at a much greater velocity than the other wheel which causes the wheels to shimmy. In addition, in some circumstances, the prior art double wheels tend to shimmy when the carrier is traveling in a linear direction and has achieved a certain velocity. It is believed that the shimmying results during linear travel are due to the inherent instability of the wheel system. The shimmying of the wheels is caused by one wheel turning much faster than the other wheel, then the other wheel turns faster than the one wheel, and so forth.
As mentioned previously, the shimmying of the wheels causes the entire carrier to vibrate and become difficult to maneuver. Therefore, there is a need for a double wheel caster which does not shimmy when turning corners or during linear travel.
The present invention overcomes many of the disadvantages inherent in the above-described double wheel casters by providing a double wheel caster wherein the support rod is rotatably mounted on the carrier and the caster wheels are mounted on the support rod with a slight press or friction fit. In the present invention, the wheels rotate in unison with the support rod because of the friction fit. The friction fit inhibits but does not prevent the wheels from rotating with respect to each other to thereby prevent one wheel from turning significantly faster than the other to reduce or prevent shimmying. Consequently, use of the present invention results in a stable transport carrier which does not shimmy during linear or arcuate travel.